This invention relates generally to grommets, and more particularly to an aircraft control cable fairlead grommet of one piece construction which can be installed with the control cable in place.
Fair lead grommets are employed to protect aircraft control cables wherever the cable penetrates a bulkhead or cable support is required. Control cables, of course, are exciteable at their natural frequency and multiples thereof. Unless restrained, large cable excursions not only damages the cables but may damage adjacent equipment. Control cables are normally restrained by running them through a fairlead and to protect the cable from chafing a fairlead grommet is installed between the cable and the fairlead.
While many innovative grommet designs are available, none of the available grommets function satisfactorily in an environment where condensation occurs on the control cable which may later freeze and form ice. Particularly poor performers in this environment are the close fitting grommets, and particularly those having an hour-glass shaped bore. Ice formed on the cable jams in the conical shape of the bore when the cable is moved in the proper direction. While ice does not generally adhere well to the plastic material used in the grommet, it readily adheres to the control cable and if the grommet is provided with slots and crevices, the ice will form in these voids and lock the cable without need for strong adhesion to the plastic material. Slots, crevices, and voids are most common with multiple element grommets.
In summary, contemporary aircraft control cable fairlead grommets function poorly when exposed to condensation followed by icing conditions. Also, some grommets are difficult to replace without removing the control cable.